1. Field of the Invention
The present invention relates to compositions for inhibiting corrosion of metals which are low foaming in the presence of aqueous media.
2. Description of the Prior Art
Corrosion is a major problem in automotive and industrial systems where major or minor amounts of water come into contact with metals such as iron, steel and ferrous alloys. Such structures as pipelines, storage tanks and internal combustion engines frequently present corrosion problems when in contact with aqueous media, or with non-aqueous media which is subject to condensation of water from the air.
Inhibitors are used to prevent corrosion in such systems. The greatest application of inhibitors is in aqueous cutting and grinding fluids where, because of the high volume of fluid and the high speed of the largely automatic tools, foam is a severe problem. Also in the tapping of aluminum or in high speed grinding or polishing of aluminum, foam, corrosion, and staining are a combined problem.
In order to inhibit corrosion in metals which are exposed to aqueous media, a large range of materials has been employed. Among the systems which have been used are hydrocarbon based systems, which are undesirable from standpoints of cost and safety, and nitrite based systems which present environmental problems. Recently, systems based on long chain fatty acids have been used; such systems are disclosed in U.S. Pat. Nos. 3,981,682, 4,614,600 and 4,683,081.
U.S. Pat. No. 3,981,682 discloses the use of cyclohexene dicarboxylic acids for preventing corrosion in systems containing largely hydrocarbon materials. Amine condensates of such acids are disclosed for rust inhibition in U.S. Pat. Nos. 4,614,600 and 4,683,081.
Inhibition in internal combustion cooling systems with or without the addition of ethylene glycol as an anti-freeze is a major inhibitor problem, and particularly for aluminum. The inhibitors used must not foam excessively. Dicarboxylic acid by itself is particularly effective as an inhibitor, as noted in U.S. Pat. No. 3,931,029, but presents a major foam problem.
While cyclohexene dicarboxylic acids of the type disclosed in U.S. Pat. No. 3,981,682 provide satisfactory corrosion inhibition in systems containing both major and minor amounts of water, these materials present foaming problems as the amount of water in the system increases. Such problems render cyclohexene dicarboxylic acids undesirable in systems with large amounts of water, such as acid solutions used to increase production in oil wells and other operations where ferrous metal surfaces are exposed to strongly acidic environments, such as pickling baths and industrial cleaning.
Other dicarboxylic acids useful in providing rust and corrosion protection in cutting and grinding fluids are the C.sub.10, C.sub.12, and C.sub.14 -bis aliphatic dicarboxylic acids. However, they present problems because, in their concentrated form, they are difficult to solubilize in oil and water, and on dilution in tap water they are susceptible to undesirable precipitation, due to hardness.
The partial esters of C.sub.21 -dicarboxylic acids have been used as combined surfactants and rust inhibitors in cutting fluids. However, they hydrolyze at the pH of the fluids, and thus promote foam.